Multiphysics Analysis of the Wendelstein 7-X Actively Cooled Scraper Element

The Wendelstein 7-X stellarator experiment is scheduled to start operation in mid- 2015, and to move to steady-state operation in 2019. During this steady-state operation, certain plasma scenarios have been shown to produce heat fluxes that exceed the technological limits on the edges of the divertor target elements. The addition of a so-called scraper element (SE) in the ten divertor locations is being investigated in order to reduce the heat load on these divertor target edges. The ANSYS commercial multiphysics package is used to model the performance of the SE under predicted operational conditions. Computational fluid dynamics (CFD) modeling is performed to analyze the hydraulic and thermal characteristics of the water-cooled SE under thermal loading using the ANSYS CFX software. This multiphysics modeling is performed for the entire SE to ensure that the total pressure drop in the cooling water circuits, the increase in water temperature, and the peak temperature in the CFC all satisfy the design requirements. Because the contour of the SE surface must be machined to a sub-millimeter precision, it is important to determine the amount of thermal expansion experienced by the entire SE. The thermal-hydraulic results are imported into ANSYS Mechanical to perform the thermal-structural analysis. The thermal deformation of the SE is examined to confirm that the component’s position will remain within its operational limits.